The present invention relates to a method and device for shading correction in video printers.
A video printer comprises a TV camera for obtaining an image of a subject, for example, pictures, documents or figures, as image data, image processing means for processing the image data from the TV camera, and printing means including an image display device such as a CRT display device on which the processed image data are displayed as a visible image, to which photographic paper is exposed to make a video print of the subject.
In such a video printer as well as the various optical image producing instruments, the image provided for the photographic exposure is shaded in compliance with the optical characteristic of the TV camera lens, the photoelectric transfer characteristic of the image sensor or pick-up tube of the TV camera, the luminance characteristic of the exposure CRT, the optical characteristics of the printing lens, etc., or various combinations thereof.
For effective shading correction in video printers. TV cameras and exposure CRTs have to be finely regulated in their characteristics. Such fine regulation demands skill and, therefore, is quite troublesome.